JP2023116754A - Biaxially oriented polypropylene-based film - Google Patents

Abstract

To provide a biaxially oriented polypropylene-based film which exhibits excellent adhesion in vapor deposition, coating and lamination with other film without impairing excellent transparency and mechanical characteristics inherent in the biaxially oriented polypropylene-based film, has good slipperiness and blocking resistance, and is suitable as a processing raw fabric.SOLUTION: A biaxially oriented polypropylene-based film has a base material layer (A) including a polypropylene-based resin as a main component, a surface layer (B) on one surface of the base material layer (A), and a surface layer (C) on a surface opposite to the surface layer (B) of the base material layer (A), wherein the surface layer (B) satisfies the following (1) to (5), and the surface layer (C) satisfies the following (6) and(7). (1) Wetting tension is 38 mN or more, (2) surface resistance value is 14.0 LogΩ or more, (3) arithmetic average roughness (Ra) is 3.0 or more and 5.5 nm or less, (4) Martens hardness is 248 N/mm2 or less, (5) center plane average roughness (SRa) is 0.010 or more and 0.026 μm or less, (6) center plane average roughness (SRa) is 0.020 μm or more, and (7) Martens hardness is 270 N/mm2 or more.SELECTED DRAWING: None

Description

The present invention relates to biaxially oriented polypropylene-based films. In detail, it is suitable for processing such as deposition of inorganic and organic substances, coating, lamination with other component films, etc., with excellent adhesion to deposited films, coating films, and adhesives, and less wrinkles and blocking on rolls. It relates to a biaxially oriented polypropylene film.

BACKGROUND ART Conventionally, biaxially oriented polypropylene films have been widely used as packaging materials for various articles such as foods and textiles because of their excellent transparency and mechanical properties. However, as a problem of polypropylene-based film, for example, since polypropylene-based resin is non-polar, its surface energy is small. It has been pointed out that the adhesion is not sufficient.

In particular, when forming a thin film layer by vapor deposition or coating, not only adhesion strength but also the problem that a thin film cannot be formed due to projections due to surface irregularities, resulting in poor barrier properties and the like. On the other hand, biaxially oriented polypropylene films have poor slipperiness due to their excellent flexibility and flatness, and blocking occurs when films stick together. As a result, the formed surface irregularities result in insufficient thin film formation by vapor deposition or coating, leading to defects such as barrier properties.

Furthermore, since biaxially oriented polypropylene film is used for various food packaging, an antistatic agent is incorporated into the film so that powders and dry materials do not stick due to static electricity. It is common to increase However, the presence of this antistatic agent on the surface of the film causes the coating to repel the solution and is unsatisfactory.

Various methods have been proposed as countermeasures against such problems. A method for improving slipperiness without using an antiblocking agent that is substantially inorganic or organic has been disclosed (see, for example, Patent Document 1, etc.). However, since only homopolypropylene with high stereoregularity is used, the surface is hard, and adhesion to thin films and coating layers after processing such as vapor deposition, coating, and lamination is not taken into consideration.

On the other hand, a method is disclosed in which antistatic agents are eliminated as much as possible and unevenness is formed on the surface layer of the film to improve the adhesiveness in lamination with ink or films of other members (see, for example, Patent Document 2).
However, higher requirements are being made for barrier properties and workability after thin film formation by vapor deposition or coating.

WO2007/094072 WO2018/142983

The present invention provides superior adhesion to adhesives in deposition films, coating films, and lamination with other component films without impairing the excellent transparency and mechanical properties inherent in biaxially oriented polypropylene films. An object of the present invention is to provide a biaxially oriented polypropylene film which is excellent in slipperiness and winding quality during processing.

The present invention, which has solved the above problems, comprises a substrate layer (A) containing a polypropylene-based resin as a main component, a surface layer (B) on one side of the substrate layer (A), and a substrate layer ( A) has a surface layer (C) on the opposite side of the surface layer (B), the surface layer (B) satisfies the following (1) to (5), and the surface layer (C) has the following ( 6) A biaxially oriented polypropylene film that satisfies (7).
(1) Wetting tension is 38 mN or more.
(2) The surface resistance value is 14.0 LogΩ or more.
(3) Arithmetic mean roughness (Ra) is 3.0 or more and 5.5 nm or less.
(4) Martens hardness is 248 N/mm ² or less.
(5) The central surface average roughness (SRa) is 0.010 or more and 0.026 μm or less.
(6) The center plane average roughness (SRa) is 0.020 μm or more.
(7) Martens hardness is 270 N/mm ² or more.

In this case, it is preferable that the dynamic friction coefficient of the biaxially oriented polypropylene film is 0.6 or less.

In this case, it is preferable that the biaxially oriented polypropylene film has a haze value of 5% or less.

Furthermore, in this case, the maximum peak height Rp+maximum valley depth Rv of the surface layer (B) is preferably 30 nm or more and 50 nm or less.

Furthermore, in this case, it is preferable that the biaxially oriented polypropylene film has an air release time of 10 seconds or less.

Furthermore, in this case, it is preferable that the thickness of the biaxially oriented polypropylene film is 9 μm or more and 200 μm or less.

Furthermore, in this case, a laminate of the biaxially oriented polypropylene film and the unstretched polyethylene film is suitable.

Furthermore, in this case, it is preferable that the lamination strength of the laminate is 2.0 g/15 mm or more.

Without impairing the excellent transparency and mechanical properties inherent in the biaxially oriented polypropylene film of the present invention, vapor deposition, coating, thin films and coating layers after lamination with other films, coating layers with other films, and It exhibited excellent adhesion, had good slipperiness and anti-blocking properties, and was suitable for the raw fabric to be processed.

It is an explanatory view of the installation of the device and the sample film used to measure the air release time (seconds).

The biaxially oriented polypropylene film of the present invention comprises a base layer (A) containing a polypropylene resin as a main component, a surface layer (B) on one side of the base layer (A), and a base layer ( A) has a surface layer (C) on the opposite side of the surface layer (B), the surface layer (B) satisfies the following (1) to (5), and the surface layer (C) has the following ( 6) It satisfies (7).
(1) Wetting tension is 38 mN or more.
(2) The surface resistance value is 14.0 LogΩ or more.
(3) Arithmetic mean roughness (Ra) is 3.0 or more and 5.5 nm or less.
(4) Martens hardness is 248 N/mm ² or less.
(5) The central surface average roughness (SRa) is 0.010 or more and 0.026 μm or less.
(6) The center plane average roughness (SRa) is 0.020 μm or more.
(7) Martens hardness is preferably 270 N/mm ² or more.
Here, the wetting tension of the surface layer (B) represents the numerical value of the surface tension (mN/m) of the mixed solution reagent determined to wet the film surface, and is related to the wettability of the printing ink or adhesive. be.
The surface resistance value of the surface of the surface layer (B) depends on the amount of antistatic agent present on the surface, and the smaller the amount of antistatic agent present on the surface, the greater the surface resistance value. .

The arithmetic average roughness (Ra) of the surface of the surface layer (B) is measured using a scanning probe microscope (AFM) in a dynamic mode in a range of 2 μm in both X and Y directions, After correcting the obtained image (inclination, line fitting, noise line removal), it is obtained according to the definition of arithmetic mean roughness described in JIS-B0601 (1994).
Arithmetic mean roughness (Ra) in the 2 μm square range by AFM is an index that represents the unevenness of the resin itself other than the relatively large peaks and valleys formed by anti-blocking agents and lubricants. , and adhesion to the resin in lamination and the like. A large Ra indicates that the unevenness of the surface is large, and that the surface area of the resin that adheres during processing is large, and the adhesion is improved. This is different from maximum peak height Rp+maximum valley depth Rv, which will be described later.

The surface Martens hardness of the surface layer (B) and the surface layer (C) was measured using a dynamic ultra-micro hardness tester, and the resin was measured by pushing the tip of the needle with a radius of curvature of 0.1 μm or less into the surface by about 0.1 μm. It indicates hardness. A low Martens hardness of the surface layer (B) indicates that the surface is soft, and the followability of the resin surface during processing is high, improving adhesion. A large Martens hardness of the surface layer (C) indicates that the surface is hard, and the protrusions formed by the antiblocking agent and the lubricant are less submerged, and the slipperiness and blocking resistance are maintained while the contact area is small. improves.

The central plane average roughness (SRa) of the surfaces of the surface layer (B) and the surface layer (C) is measured using a three-dimensional roughness meter at a stylus pressure of 20 mg and a measurement length of 1 mm in the X direction, Y Measured with 99 recorded lines at a feed pitch of 2 μm in the direction, a magnification of 20000 times in the height direction, and a cutoff of 80 μm, and obtained according to the definition of arithmetic average roughness described in JIS-B0601 (1994). .

The center surface average roughness (SRa) is an index that indicates the surface unevenness including relatively large peaks and valleys formed by anti-blocking agents and lubricants. blocking. When the SRa is large, the unevenness of the surface is large, and the contact area on the surface becomes small in blocking between films or sliding with metals, etc., and slipperiness and anti-blocking properties are improved.

(1) Base layer (A)
The polypropylene resin constituting the substrate layer (A) of the biaxially oriented polypropylene film of the present invention is a polypropylene homopolymer that does not contain a copolymer component, and ethylene and / or an α-olefin having 4 or more carbon atoms. A polypropylene resin copolymerized at 0.5 mol % or less can be used. The content of the copolymer component is preferably 0.3 mol % or less, more preferably 0.1 mol % or less, and most preferably polypropylene homopolymer containing no copolymer component.
When the copolymerization amount of ethylene and/or α-olefin having 4 or more carbon atoms is 0.5 mol % or less, the crystallinity and rigidity are less likely to decrease, and the heat shrinkage rate at high temperatures is less likely to increase. A blend of these resins may be used.

The mesopentad fraction ([mmmm]%) measured by ¹³ C-NMR, which is an index of the stereoregularity of the polypropylene resin constituting the base layer (A) of the biaxially oriented polypropylene film of the present invention, is 98. % or more and 99.5% or less. More preferably, it is 98.1% or more, and still more preferably 98.2% or more. If the mesopentad ratio of the polypropylene-based resin is low, the elastic modulus is low, and the heat resistance may be insufficient. 99.5% is a realistic upper limit.

The mass-average molecular weight (Mw) of the polypropylene-based resin constituting the base layer (A) of the biaxially oriented polypropylene-based film of the present invention is preferably 180,000 or more and 500,000 or less.
If it is less than 180,000, the melt viscosity is so low that it may not be stable during casting, resulting in poor film formability. When Mw exceeds 500,000, the amount of components having a molecular weight of 100,000 or less is 35% by mass, and the heat shrinkage at high temperatures is reduced.
A more preferable lower limit of Mw is 190,000, more preferably 200,000, and a more preferable upper limit of Mw is 320,000, more preferably 300,000, and particularly preferably 250,000.

The number average molecular weight (Mn) of the polypropylene resin constituting the substrate layer (A) of the biaxially oriented polypropylene film of the present invention is preferably 20,000 or more and 200,000 or less.
If it is less than 20,000, the melt viscosity is so low that it may not be stable during casting, resulting in poor film formability. If it exceeds 200,000, the heat shrinkage rate at high temperatures is reduced.
A more preferable lower limit of Mn is 30,000, more preferably 40,000, particularly preferably 50,000, and a more preferable upper limit of Mn is 80,000, more preferably 70,000, particularly preferably 60,000. be.

Moreover, Mw/Mn, which is an index of molecular weight distribution, is preferably 2.8 or more and 10 or less in the case of the polypropylene resin constituting the base material layer (A). It is more preferably 2.8 or more and 8 or less, still more preferably 2.8 or more and 6 or less, and particularly preferably 2.8 or more and 5.4 or less. Also, the lower limit is preferably 3 or more, more preferably 3.3 or more.
The molecular weight distribution of polypropylene resin can be adjusted by polymerizing components with different molecular weights in multiple stages in a series of plants, by blending components with different molecular weights offline in a kneader, or by blending catalysts with different performance. It can be adjusted by polymerization or by using a catalyst capable of realizing a desired molecular weight distribution.

The polypropylene resin constituting the base layer (A) of the biaxially oriented polypropylene film of the present invention has a melt flow rate (MFR; 230 °C, 2.16 kgf) is preferably 2 g/10 minutes or more and 20 g/10 minutes or less.
The lower limit of the MFR of the polypropylene-based resin of the substrate layer (A) is more preferably 3 g/10 minutes, even more preferably 4 g/10 minutes, and particularly preferably 5 g/10 minutes. The upper limit of the MFR of the polypropylene-based resin of the substrate layer (A) is more preferably 15 g/10 minutes, and even more preferably 12 g/10 minutes.
When the Mw/Mn and MFR of the polypropylene-based resin constituting the base material layer (A) are within this range, the heat shrinkage rate at high temperatures can be kept small, and the adhesion to the cooling roll is good. Excellent film formability.

(2) Surface layer (B)
The surface layer (B) of the biaxially oriented polypropylene film of the present invention preferably has a surface arithmetic mean roughness (Ra) of 3.0 to 5.5 nm. If the arithmetic mean roughness (Ra) is less than 3.0 nm, the surface area of the surface layer (B) is small, and there arises a problem that the adhesion is lowered in processing such as vapor deposition, coating, and lamination. When the arithmetic mean roughness (Ra) exceeds 5.5 nm, the surface unevenness is large, voids occur during vapor deposition or coating, and the barrier properties and the like become poor.
The arithmetic mean roughness (Ra) of the surface layer (B) is more preferably 3.2 nm or more, still more preferably 3.3 nm or more, particularly preferably 3.5 nm or more, and most preferably 4.0 nm or more.
In order for the arithmetic mean roughness (Ra) of the surface layer (B) to be 3.0 or more and 5.5 nm or less, the polypropylene resin composition forming the surface layer (B) must have a melt flow rate ( It is preferable to use a mixture of two or more polypropylene resins having different MFRs. In this case, the difference in MFR is preferably 3 g/10 minutes or more, more preferably 3.5 g/10 minutes or more.
As described above, if the difference in melt flow rate (MFR) between two or more polypropylene resins in a mixture of polypropylene resins is different, the crystallization rate and degree of crystallinity of each polypropylene resin will be different, so the surface It is presumed that unevenness is likely to be generated on the surface. However, if the crystallinity of the polypropylene-based resin is high or the cooling rate of the unstretched sheet during film production is slow, surface unevenness due to spherulites will increase, and the stretching temperature will be too high during longitudinal or transverse stretching. If the surface unevenness becomes large, the arithmetic mean roughness (Ra) may exceed 5.5 nm, so caution is required.
Polypropylene obtained by copolymerizing ethylene and/or an α-olefin having 4 or more carbon atoms can also be used as the polypropylene resin having a smaller MFR. Examples of α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. In addition, maleic acid or the like having polarity may be used as another copolymerization component.
The total content of ethylene and/or α-olefins having 4 or more carbon atoms and other copolymer components is preferably 8.0 mol % or less. If it is copolymerized in excess of 8.0 mol %, the film may turn white and have a poor appearance, or may become sticky and difficult to form.
Two or more of these resins may be blended for use. When blended, individual resins may be copolymerized in excess of 8.0 mol%, but the blend preferably contains 8.0 mol% or less of monomers other than propylene in monomer units. .
As the polypropylene-based resin having a larger MFR, the above-mentioned copolymerized polypropylene can be used, and a homopolypropylene resin can also be used.
The mixing ratio of the polypropylene resin with a smaller MFR and the polypropylene resin with a larger MFR is preferably in the range of 1% by weight/99% by weight to 49% by weight/51% by weight, and 1% by weight/99% by weight to 30% by weight. A range of weight %/70 weight % is more preferred, and a range of 1 weight %/99 weight % to 10 weight %/90 weight % is even more preferred.

Further, the polypropylene resin composition constituting the surface layer (B) of the biaxially oriented polypropylene film of the present invention preferably has an MFR of 1.0 g/10 min or more and 10.0 g/10 min or less. The lower limit of the MFR of the polypropylene-based resin composition of the surface layer (B) is more preferably 2.0 g/10 minutes, still more preferably 3.0 g/10 minutes, and 4.0 g/10 minutes. It is particularly preferred to have The upper limit of the MFR of the polypropylene-based resin composition that constitutes the surface layer (B) is more preferably 9.0 g/10 minutes, still more preferably 8.0 g/10 minutes, and 5.5 g/10 minutes. Minutes are particularly preferred. Within this range, the film formability is good and the appearance is excellent. If the MFR of the polypropylene-based resin composition that constitutes the surface layer (B) is less than 1.0 g/10 min, the MFR of the polypropylene-based resin composition that constitutes the base layer (A) is large, and the base layer ( Since the viscosity difference between A) and the surface layer (B) increases, unevenness (raw fabric unevenness) tends to occur during film formation. When the MFR of the polypropylene-based resin composition constituting the surface layer (B) exceeds 10 g/10 minutes, the adhesion to the cooling roll deteriorates, air is entrained, and the smoothness is poor, which is the starting point of the defect. is likely to increase.

Further, the surface layer (B) of the biaxially oriented polypropylene film preferably has a center surface average roughness (SRa) measured by a three-dimensional roughness meter of 0.010 μm or more and 0.026 μm or less. The center plane average roughness (SRa) of the surface of the surface layer (B) is more preferably 0.012 μm or more and 0.025 μm or less, more preferably 0.015 μm or more and 0.025 μm or less, and 0.020 μm or more and 0.025 μm or less. 0.024 μm or less is particularly preferred. If the surface center plane average roughness (SRa) of the surface layer (B) is less than 0.010 μm, the surface unevenness is small, and the slipperiness of the film, the air release time between films, and the blocking resistance deteriorate. If the center plane average roughness (SRa) of the surface of the surface layer (B) exceeds 0.026 μm, when applying a thin film layer such as aluminum vapor deposition or coating, the thin film layer may be penetrated by an anti-blocking agent or the thin film may be formed on the side surface of the convex portion. may not be formed, resulting in reduced barrier properties and poor adhesion. There are several methods for making the center surface average roughness (SRa) of the surface layer (B) within a specified range, and it is possible to adjust the average particle size and the amount of the antiblocking agent added.
As the anti-blocking agent, inorganic particles such as silica, calcium carbonate, kaolin, and zeolite, and organic particles such as acrylic, polymethacrylic, and polystyrene particles can be appropriately selected and used. Among these, it is particularly preferable to use silica and polymethacrylic particles. The average particle size of the antiblocking agent is preferably 1.0 µm or more and 3.0 µm or less, more preferably 1.0 µm or more and 2.7 µm or less. The method of measuring the average particle diameter as used herein is to take a photograph with a scanning electron microscope, measure the Feret diameter in the horizontal direction using an image analyzer, and display the average value.
The amount of the antiblocking agent added to the surface layer (B) and the surface layer (C) is such that the haze, dynamic friction coefficient, center surface average roughness (SRa), and air release time are within the predetermined ranges. is adjusted, there is no particular limitation.

The surface resistance of the surface layer (B) of the biaxially oriented polypropylene film of the present invention is preferably 14 logΩ or more. When the surface resistance value is 14 logΩ or more, the adhesiveness to vapor deposition films, coating films, and adhesives is improved. More preferably, the surface resistance value is 14.5 LogΩ or more, and even more preferably 15 LogΩ or more. If the surface resistance value is less than 14 logΩ, not only does the adhesion decrease, but also the antistatic agent that bleeds onto the surface layer (B) repels the coating, resulting in poor coating. In order to obtain a surface resistance value of 14 logΩ or more, it is possible to minimize the use of additives such as antistatic agents and antifogging agents. In addition, the additives contained in the substrate layer (A) may bleed onto the surface of the surface layer (B), so care must be taken.

The surface wetting tension of the surface layer (B) of the biaxially oriented polypropylene film of the present invention is preferably 38 mN/m or more. When the wetting tension is 38 mN/m or more, the adhesion with the adhesive used for lamination with vapor deposition films, coating films, and films of other members is improved. In order to increase the wetting tension to 38 mN/m or more, additives such as antistatic agents and surfactants are usually used. Physicochemical surface treatments such as corona treatment and flame treatment are preferably performed.
For example, in corona treatment, it is preferable to use a preheated roll and a treatment roll to perform discharge in the air.

The Martens hardness of the surface layer (B) of the biaxially oriented polypropylene film of the present invention is preferably 248 N/mm ² or less, more preferably 245 N/mm ² or less, and still more preferably 240 N/mm ² or less. , particularly preferably 235 N/mm ² or less, most preferably 230 N/mm ² or less.
When the Martens hardness exceeds 248 N/mm ² , the surface is hard, and the followability of the resin surface during processing deteriorates, resulting in a decrease in adhesion. The Martens hardness of 248 N/mm ² or less can be achieved by adding ethylene and/or an α-olefin having 4 or more carbon atoms and other copolymer components. The Martens hardness can also be lowered by lowering the orientation of the molecular chains by lowering the draw ratio of the film.
The surface layer (B) of the biaxially oriented polypropylene film of the present invention preferably has a Martens hardness of 200 N/mm ² or more, more preferably 210 N/mm ² or more.

The maximum peak height Rp+maximum valley depth Rv of the surface of the surface layer (B) of the biaxially oriented polypropylene film of the present invention by AFM is preferably 30 or more and 50 nm or less. The lower limit of the maximum peak height Rp + maximum valley depth Rv on the surface of the surface layer (B) is more preferably 32 nm, still more preferably 35 nm, and particularly preferably 38 nm. The upper limit of the maximum peak height Rp + maximum valley depth Rv on the surface of the surface layer (B) is more preferably 48 nm, particularly preferably 45 nm. The maximum peak height Rp and the maximum valley depth Rv are not due to the antiblocking agent, but due to the unevenness of the resin itself. When the maximum peak height Rp+maximum valley depth Rv is 30 nm or more, air escape and blocking resistance due to contact with the surface layer (C) in the roll state are improved. Moreover, the surface area of the surface layer (B) is increased, and the adhesion to the deposition layer and the coating layer is improved.
However, since the air escape and blocking resistance are greatly related to the center surface roughness (SRa) measured by a three-dimensional roughness meter, which will be described later, even if the maximum peak height Rp and the maximum valley depth Rv are less than 30 nm B) If the center surface roughness (SRa) of the surface layer (C) is large, it is possible that air escape and blocking resistance are good. When the maximum peak height Rp+maximum valley depth Rv is 50 nm or less, the surface unevenness does not become too large, the vapor deposition layer and the coating layer are less likely to come off, and barrier properties and the like are improved.

(3) Surface layer (C)
The surface layer (C) of the biaxially oriented polypropylene film of the present invention preferably has a center surface average roughness (SRa) of 0.020 μm or more measured by a three-dimensional roughness meter. The center plane average roughness (SRa) of the surface of the surface layer (C) is more preferably 0.022 μm or more, still more preferably 0.025 μm, and particularly preferably 0.028 μm.
If the surface center plane average roughness (SRa) of the surface layer (C) is less than 0.020 μm, the surface unevenness is small, and the slipperiness of the film, the air release time between films, and the blocking resistance deteriorate. There are several methods for making the center surface average roughness (SRa) of the surface layer (C) within a specified range, and it is possible to adjust the average particle size and the amount of the antiblocking agent added.
The surface layer (C) of the biaxially oriented polypropylene film of the present invention preferably has a center surface average roughness (SRa) of 0.040 μm or less measured by a three-dimensional roughness meter.

The surface layer (C) of the biaxially oriented polypropylene film preferably has a Martens hardness of 270 N/mm ² or more. It is more preferably 275 N/mm ² or more, still more preferably 280 N/mm ² or more, and particularly preferably 285 N/mm ² or more.
If the Martens hardness is less than 270 N/mm ² , the surface is soft and the added anti-blocking agent sinks into the resin, resulting in poor lubricity and anti-blocking properties. In order to achieve a Martens hardness of 270 N/mm ² or more, it is preferable to use polypropylene obtained by copolymerizing ethylene and/or an α-olefin having 4 or more carbon atoms at 0.5 mol% or less, but 0.1 mol % or less is more preferred, and complete homopolypropylene containing no copolymer components is most preferred. Further, the mesopentad fraction ([mmmm]%) of the polypropylene constituting the material is set to 98% or more, and the crystallinity is increased, so that the Martens hardness can be increased.
The surface layer (C) of the biaxially oriented polypropylene film preferably has a Martens hardness of 350 N/mm ² or less.

The polypropylene resin used in the present invention is obtained by polymerizing raw material propylene using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, it is preferable to use a Ziegler-Natta catalyst in order to eliminate heterogeneous bonds, and to use a catalyst capable of polymerizing with high stereoregularity.
As a method for polymerizing propylene as a raw material, a known method may be adopted. A method of adding a catalyst to a monomer and polymerizing in a gas phase, or a method of polymerizing by combining these methods can be used.

The substrate layer (A) and/or the surface layer (B) and/or the surface layer (C) of the biaxially oriented polypropylene film of the present invention may contain additives and other resins. . Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifog agents, flame retardants, inorganic or organic fillers, and the like. Other resins include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers that are copolymers of propylene and ethylene and/or α-olefins having 4 or more carbon atoms, and various elastomers. These are polymerized sequentially using a multi-stage reactor, blended with polypropylene resin in a Henschel mixer, or prepared in advance using a melt kneader and diluted with polypropylene to a predetermined concentration. Alternatively, the entire amount may be previously melted and kneaded before use.

(3) Biaxially oriented polypropylene film The biaxially oriented polypropylene film of the present invention has a three-layer structure of surface layer (B) / base layer (A) / surface layer (C), surface layer (B) / intermediate Four layers of layers (D/base layer (A)/intermediate layer (D)/surface layer (C), surface layer (B)/base layer (A)/intermediate layer (D)/surface layer (C)) It may be a structure or a multi-layered structure.

The thickness of the entire biaxially oriented polypropylene film of the present invention is preferably 9 μm or more and 200 μm or less, more preferably 10 μm or more and 150 μm or less, still more preferably 12 μm or more and 100 μm or less, and particularly preferably 15 μm or more and 80 μm or less.

As the ratio of the thickness of the surface layer (B) to the thickness of the substrate layer (A) in the biaxially oriented polypropylene film of the present invention, the thickness of the entire surface layer (B) / the thickness of the entire substrate layer (A) is , preferably 0.01 or more and 0.50 or less, more preferably 0.02 or more and 0.40 or less, further preferably 0.03 or more and 0.30 or less, and 0.01 or more and 0.50 or less. 04 or more and 0.20 or less is particularly preferable. When the ratio of thickness of the entire surface layer (B)/thickness of the entire base layer (A) exceeds 0.50, the shrinkage tends to increase.

The ratio of the thickness of the surface layer (C) to the thickness of the substrate layer (A) in the biaxially oriented polypropylene film is such that the thickness of the entire surface layer (C)/thickness of the entire substrate layer (A) is 0. It is preferably 0.01 or more and 0.50 or less, more preferably 0.02 or more and 0.40 or less, further preferably 0.03 or more and 0.30 or less, and 0.04 or more. , 0.20 or less. If the ratio of the total thickness of the surface layer (C)/the total thickness of the substrate layer (A) exceeds 0.50, the haze may increase depending on the amount of the antiblocking agent added, and the transparency may deteriorate.

The thickness of the substrate layer (A) or the total thickness of the substrate layer (A) and the intermediate layer (D) is preferably 50% or more and 99% or less, more preferably 99% or less, of the thickness of the entire film. 60% or more and 97% or less, particularly preferably 70% or more and 90% or less, most preferably 80% or more and 92% or less.

The haze of the biaxially oriented polypropylene film of the present invention is preferably 5% or less, more preferably 0.2% or more and 5.0% or less, still more preferably 0.3 or more and 4.5%, and 0.4 % or more, particularly preferably 4.0%. Within the above range, it may be easy to use in applications where transparency is required. Haze tends to be worsened, for example, when the stretching temperature and heat setting temperature are too high, when the cooling roll temperature is high and the cooling rate of the unstretched (original) sheet is slow, and when the low molecular weight component is too large, these are adjusted. By doing so, it is possible to make it within the above range. A method for measuring haze will be described later.

The longitudinal tensile modulus of the biaxially oriented polypropylene film of the present invention is preferably 1.8 or more and 4.0 GPa or less, more preferably 2.0 GPa or more and 3.7 GPa or less. .1 GPa or more and 3.5 GPa or less is more preferable, and 2.2 or more and 3.4 GPa or less is particularly preferable.
The transverse tensile modulus of the biaxially oriented polypropylene film of the present invention is preferably 3.8 GPa or more and 8.0 GPa or more, more preferably 4.0 GPa or more and 7.5 GPa or less. .1 GPa or more and 7.0 GPa or less is more preferable, and 4.2 GPa or more and 6.5 GPa or less is particularly preferable. If the tensile modulus is within the above range, the film becomes stiff and can be used even if the film thickness is small, so it is possible to reduce the amount of film used. A method for measuring the tensile modulus will be described later.

In the biaxially oriented polypropylene film of the present invention, the heat shrinkage rate in the longitudinal direction at 150° C. is preferably 0.2 to 15.0%, and preferably 0.3% to 13.0%. is more preferably 0.5% or more and 11.0% or less, and particularly preferably 0.5% or more and 9.0% or less. If the heat shrinkage rate is within the above range, the film can be said to be excellent in heat resistance and can be used in applications where there is a possibility of being exposed to high temperatures. If the 150° C. heat shrinkage rate is up to about 1.5%, it is possible, for example, by increasing the low molecular weight component and adjusting the stretching conditions and heat setting conditions. Treatment or the like is preferable.
In the biaxially oriented polypropylene film of the present invention, the lateral heat shrinkage at 150° C. is preferably 0.5% or more and 30.0% or less, and 0.5% or more and 25.0% or less. is more preferably 0.5% or more and 20.0% or less, and particularly preferably 0.5% or more and 18.0% or less. If the heat shrinkage rate is within the above range, the film can be said to be excellent in heat resistance and can be used in applications where there is a possibility of being exposed to high temperatures. If the 150° C. heat shrinkage rate is up to about 1.5%, it is possible, for example, by increasing the low molecular weight component and adjusting the stretching conditions and heat setting conditions. Treatment or the like is preferable. A method for measuring the thermal shrinkage rate will be described later.

The dynamic friction coefficient of the biaxially oriented polypropylene film of the present invention is preferably 0.6 or less, more preferably 0.55 or less, and particularly preferably 0.50 or less. When the coefficient of dynamic friction is 0.6 or less, the film can be smoothly unwound from the roll film, and the printing process is easy. The coefficient of dynamic friction may be 0.1 or more. A method for measuring the coefficient of dynamic friction will be described later.

The air release time of the biaxially oriented polypropylene film of the present invention is preferably 10 seconds or less, more preferably 8 seconds or less, even more preferably 5 seconds or less, and particularly preferably 3 seconds or less. If the air-releasing time exceeds 10 seconds, air is slowly released when rolled, and wrinkles are likely to occur. The air release time may be 1 second or longer. A method for measuring the air release time will be described later.
When the biaxially oriented polypropylene film of the present invention is wound into a film roll having a width of 300 mm and a winding length of 800 m or more, it is suitable for transportation, vapor deposition processing, coating processing, and bag making processing.
When the biaxially oriented polypropylene film of the invention was wound up with a width of 500 mm and a winding length of 1000 m, and the wrinkles on the roll surface layer were visually evaluated according to the following criteria, there were weak wrinkles, but the tension of the film pulled out was 20 N / m. It is preferable that wrinkles disappear when a degree is applied, and it is more preferable that there are no wrinkles.

When the gas barrier properties and design properties of the biaxially oriented polypropylene film of the invention are desired to be enhanced, a layer made of aluminum, polyvinylidene chloride, nylon, ethylene-vinyl alcohol copolymer, or polyvinyl alcohol, especially a thin layer, is provided and used. is preferred.
It is preferable that the aluminum thin film layer is only partially peeled from the aluminum thin film provided on the surface of the biaxially oriented polypropylene film of the invention, and more preferably that the aluminum thin film layer is not partially peeled. When a coat layer is provided on the surface of the biaxially oriented polypropylene film, it is preferable that the coating layer has only a small amount of cissing, and more preferably that the coating layer has no cissing.
In addition, the biaxially oriented polypropylene film of the present invention or a thin film layer provided thereon, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, unstretched film made of polyester, uniaxially stretched It is preferable to use a laminate of a film and a biaxially stretched film and process it into a packaging bag.
The laminate strength of the laminate of the biaxially oriented polypropylene film and the unstretched polyethylene film of the present invention is preferably 2.0 N/15 mm or more, more preferably 2.3 N/mm or more, and further preferably 2.5 N/mm or more. Preferably, 2.8 N/mm or more is particularly preferable. The laminate strength should be 5 N/mm or less. A method for measuring the lamination strength will be described later.

(4) Production method The biaxially oriented polypropylene film of the present invention comprises a polypropylene resin composition constituting the base layer (A), a polypropylene resin composition constituting the surface layer (B), and a surface layer (C). The polypropylene resin composition is melt-extruded by separate extruders, co-extruded from a die, cooled with a cooling roll to form an unstretched sheet, and the unstretched sheet is longitudinally (MD) and widthwise. It can be obtained by stretching to (TD) and then heat-setting. In addition, it is preferable to extrude so that the surface layer (B) is in contact with the cooling roll. When the surface layer (B) becomes the opposite side in contact with the cooling roll, the polypropylene resin is slowly cooled, the degree of crystallinity increases, and the surface unevenness due to the spherulites increases the arithmetic mean roughness ( Ra) may become too large.
The melt extrusion temperature is preferably about 200 to 280° C. In order to obtain a laminated film with a good appearance without disturbing the layers within this temperature range, the polypropylene resin composition constituting the base layer (A) and the surface layer It is preferable that the viscosity difference (MFR difference) of the polypropylene-based resin composition constituting (B) is 6.0 g/10 minutes or less. If the viscosity difference is more than 6 g/10 minutes, the layers tend to be disordered and the appearance is poor. It is more preferably 5.5 g/10 minutes or less, still more preferably 5.0 g/10 minutes or less.

The cooling roll surface temperature is preferably 25° C. or higher and 35° C. or lower, more preferably 27° C. or higher and 33° C. or lower. If the cooling roll temperature exceeds 35°C, the degree of crystallinity of the polypropylene-based resin increases, and the surface roughness of the formed spherulites may cause the arithmetic mean roughness (Ra) of the surface of the surface layer (B) to become too large. be.

The lower limit of the draw ratio in the machine direction (MD) is preferably 3 times, more preferably 3.5 times. If it is less than the above, the film thickness may become uneven. The upper limit of the MD draw ratio is preferably 8 times, more preferably 7 times. When the above is exceeded, it may become difficult to carry out subsequent TD stretching. The lower limit of the MD stretching temperature is preferably 120°C, more preferably 125°C, and still more preferably 130°C. If it is less than the above, the mechanical load may increase, the thickness unevenness may increase, and the surface of the film may become rough. The upper limit of the MD stretching temperature is preferably 160°C, more preferably 155°C, still more preferably 150°C. A higher temperature is preferable for lowering the heat shrinkage, but it may adhere to the rolls, making it impossible to stretch or roughening the surface.

The lower limit of the draw ratio in the width direction (TD) is preferably 4 times, more preferably 5 times, and still more preferably 6 times. If it is less than the above, thickness unevenness may occur. The upper limit of the TD draw ratio is preferably 20 times, more preferably 17 times, still more preferably 15 times, and particularly preferably 12 times. If the above is exceeded, the heat shrinkage rate may increase, or breakage may occur during stretching. The preheating temperature in TD stretching is preferably set 5 to 15° C. higher than the stretching temperature in order to quickly raise the film temperature to the vicinity of the stretching temperature. The lower limit of the TD stretching temperature is preferably 150°C, more preferably 155°C, even more preferably 158°C, and particularly preferably 160°C. If it is less than the above, it may be broken without sufficiently softening, or the heat shrinkage rate may increase. The upper limit of the TD stretching temperature is preferably 170°C, more preferably 168°C, still more preferably 165°C. In order to reduce the heat shrinkage, the temperature is preferably high, but if it exceeds the above, the low molecular weight component melts and recrystallizes, not only lowering the orientation but also surface roughening and whitening of the film.

The stretched film is heat set. The lower limit of the heat setting temperature is preferably 163°C, more preferably 165°C. If it is less than the above, the heat shrinkage rate may increase. In addition, a long time of treatment is required to reduce the heat shrinkage, which may result in poor productivity. The upper limit of the heat setting temperature is preferably 176°C, more preferably 175°C. If the above is exceeded, the low-molecular-weight components may melt and recrystallize, resulting in surface roughness and whitening of the film.

It is preferable to relax (relax) at the time of heat setting. The lower limit of the relaxation rate is preferably 2%, more preferably 3%. If it is less than the above, the heat shrinkage rate may increase. The upper limit of the relaxation rate is preferably 10%, more preferably 8%. When the above is exceeded, thickness unevenness may become large.

Furthermore, in order to reduce the thermal shrinkage, the film produced by the above process can be wound into a roll and then annealed off-line.

The biaxially oriented polypropylene film thus obtained may be subjected, if necessary, to corona discharge, plasma treatment, flame treatment, etc., and then wound up with a winder to obtain the biaxially oriented polypropylene film roll of the present invention. can.

The present invention will be described in more detail below with reference to examples, but the following examples do not limit the present invention, and are included in the present invention when modified within the scope of the gist of the present invention.

(Measuring method)
Raw materials used in Examples and Comparative Examples and methods for measuring physical properties of the obtained films are as follows.

1) Mesopentad fraction ([mmmm] unit: %)
The mesopentad fraction was measured using ¹³ C-NMR. The mesopentad fraction was calculated according to the method described in "Zambelli et al., Macromolecules, Vol. 6, p.925 (1973)". ¹³ C-NMR measurement was carried out at 110° C. by dissolving 200 mg of a sample in a mixture of o-dichlorobenzene and deuterated benzene at 8:2 (volume ratio) at 135° C. using “AVANCE500” manufactured by BRUKER.

2) Melt flow rate ([MFR] g/10 minutes)
It was measured at a temperature of 230° C. and a load of 2.16 kgf according to JIS K7210.
In the case of raw material resin, pellets (powder) were weighed and used as they were.
In the case of the film, after cutting out the required amount, a sample cut into about 5 mm square was used.

3) Molecular Weight and Molecular Weight Distribution The molecular weight and molecular weight distribution of the starting resin and film were obtained by gel permeation chromatography (GPC) on the basis of monodisperse polystyrene. Measurement conditions such as columns and solvents used in GPC measurement are as follows.
Solvent: 1,2,4-trichlorobenzene Column: TSKgel GMHHR-H (20) HT x 3
Flow rate: 1.0ml/min
Detector: RI
Measurement temperature: 140°C

The number average molecular weight (Mn), mass average molecular weight (Mw), and molecular weight distribution (Mw/Mn) are the molecular weights (M _i ) at each elution position of the GPC curve obtained through the molecular weight calibration curve ( N _i ) is defined by the following equation.
Number average molecular weight: Mn = Σ (N _i · M _i ) / ΣN _i
Mass average molecular weight: Mw = Σ (N _i · M _i ² ) / Σ (N _i · M _i )
Molecular weight distribution: Mw/Mn
When the baseline was not clear, the baseline was set in the range up to the lowest point of the high-molecular-weight elution peak closest to the elution peak of the standard substance.

4) Melting peak temperature (°C), melting peak area (J/g)
Using a differential scanning calorimeter (DSC) manufactured by SII, measurement was carried out at a sample amount of 10 mg and a heating rate of 20°C/min. A melting endothermic peak temperature and a melting peak area were obtained from the DSC curve.

5) Thickness (μm)
The thickness of each of the base layer (A) and the surface layer (B) was measured by cutting out a cross section of a biaxially stretched laminated polypropylene film solidified with a modified urethane resin with a microtome and observing it with a differential interference microscope.

6) Haze (%)
Measured at 23° C. according to JIS K 7105. It was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., 300A). In addition, the measurement was performed twice and the average value was obtained.

7) Tensile modulus (GPa)
Measured according to JIS K 7127. A sample having a width of 10 mm and a length of 180 mm in the longitudinal and width directions of the film was cut out using a razor to obtain a sample. After being left for 12 hours in an atmosphere of 23°C and 65% RH, measurement was performed in an atmosphere of 23°C and 65% RH under the conditions of a chuck distance of 100 mm and a pulling speed of 200 mm/min. values were used. Autograph AG5000A manufactured by Shimadzu Corporation was used as a measuring device.

8) Thermal shrinkage rate (%)
It was measured by the following method according to JIS Z1712. The film was cut into a width of 20 mm and a length of 200 mm in each of the MD direction and the TD direction, suspended in a hot air oven at 150° C. and heated for 5 minutes. The length before and after heating was measured, and the ratio (%) of the length before heating minus the length after heating to the length before heating was determined to determine the thermal shrinkage rate.

9) Wetting tension (mN/m)
After the film was aged at 23° C. and 50% relative humidity for 24 hours according to JIS K 6768:1999, the corona-treated surface of the film was measured by the following procedure.
Step 1)
The measurement is performed in a standard laboratory atmosphere (see JIS K 7100) with a temperature of 23°C and a relative humidity of 50%.
Step 2)
Place the test piece on the substrate of the hand coater (4.1), drop a few drops of the test mixture on the test piece and immediately pull the wire bar out.
If a cotton swab or brush is used to spread the test mixture, spread the liquid quickly over an area of at least 6 ^cm2 . The amount of liquid should be such that it forms a thin layer without pooling.
Wetting tension is determined by observing the liquid film of the mixed solution for testing in a bright place and observing the state of the liquid film after 3 seconds. If the applied state is maintained for 3 seconds or more without breaking the liquid film, it means that the liquid is wet. If the wetness is maintained for 3 seconds or more, the mixture proceeds to the next higher surface tension mixture, and conversely, if the liquid film breaks in 3 seconds or less, the mixture proceeds to the next lower surface tension mixture.
Repeat this operation and select a mixture that can wet the surface of the test piece accurately in 3 seconds.
Step 3)
Use a new swab for each test. Brushes or wire bars should be cleaned with methanol and dried between uses, as residual liquid will change composition and surface tension upon evaporation.
Step 4)
The operation of selecting a mixture that can wet the surface of the test piece in 3 seconds is performed at least 3 times. The surface tension of the mixture thus selected is reported as the wetting tension of the film.

10) Surface resistance value (LogΩ)
After the film was aged at 23° C. for 24 hours, the surface layer (B) of the film was measured according to JIS K6911.

11) Dynamic Friction Coefficient In conformity with JIS K7125, surface layer (B) surfaces of two films were superimposed and measured at 23°C.

12) Air release time (seconds)
As shown in FIG. 1, a biaxially oriented polypropylene film as the film 4 is placed on the base plate 1 so that the surface layer (B) faces upward. Next, the film presser 2 is placed on the film 4 and fixed to fix the film 4 while applying tension. Next, a biaxially oriented polypropylene film as the film 5 is placed on the film presser 2 so that the surface layer (C) faces downward. Next, the film retainer 8 is placed on the film 5, and the film retainers 8 and 2 and the base plate 1 are fixed using the screws 3.
Next, the cavity 2 a provided in the film presser 2 and the vacuum pump 6 are connected through the hole 2 c provided in the film presser 2 and the pipe 7 . When the vacuum pump 6 is driven, tension is applied to the film 5 by being sucked into the cavity 2a. At the same time, the overlapping surfaces of the film 4 and the film 5 are also decompressed through the holes 2d provided in the circumferential shape of the film presser 2, so that the films 4 and 5 are brought into close contact with each other from the outer periphery on the overlapping surfaces. start.
The state of close contact can be easily known by observing the interference fringes from above the overlapping surfaces. Then, the time (seconds) from the occurrence of the interference fringes on the periphery of the superimposed surfaces of the film 4 and the film 5 to the spread of the interference fringes on the front surface of the overlapping surfaces until the movement stops was measured. is the deflation time. In addition, the measurement is repeated 5 times by replacing the two films, and the average value is used. That is, the shorter the time (seconds), the better the winding characteristics of the film.

13) Martens hardness HMs (N/mm ² )
The obtained film was cut into a square of about 2 cm, and the opposite side of the measurement surface was fixed on a glass plate having a thickness of about 1 mm with an adhesive. and humidified. This sample was measured using a dynamic ultra-micro hardness tester ("DUH-211" manufactured by Shimadzu Corporation) under the following measurement conditions according to a method in accordance with ISO14577-1 (2002). Measurement was performed by changing the position of the film. The measurement was performed 10 times, and the average value of 8 points excluding the maximum and minimum was obtained.

<Measurement conditions>
(setting)
・Measurement environment: temperature 23°C, relative humidity 50%
・Test mode: Load-unload test ・Indenter used: Ridge angle 115 degrees, triangular pyramid indenter (made by diamond)
・Indenter elastic modulus: 1.140 × 106 N / mm ²
・Indenter Poisson's ratio: 0.07
・Cf-Ap, As correction: Yes (condition)
・Test force: 0.10 mN
・Load speed: 0.0050mN/sec
・Load holding time: 5 sec
・Unloading holding time: 0 sec
Martens hardness is the test force-indentation depth curve, and the depth between the test force 50% F and 90% F (F = 0.10 mN) is proportional to the square root of the test force. Obtained from the formula (1).
Martens hardness HMs=1/(26.43×m ² ) (1)

14) Center surface average roughness ([SRa] μm)
The central surface average roughness (SRa) of the obtained film is measured using a three-dimensional roughness meter (manufactured by Kosaka Laboratory Co., Ltd., model number ET-30HK), with a stylus pressure of 20 mg, and a measurement length of 1 mm in the X direction. , Feed speed 100 μm / sec, Y direction feed pitch 2 μm, number of recording lines 99, height direction magnification 20000 times, cutoff 80 μm Measurement was performed, and the arithmetic average roughness described in JIS-B0601 (1994) was measured. Calculated according to the definition.
Arithmetic mean roughness (SRa) was evaluated by the average value of three trials.

15) Arithmetic mean roughness ([Ra] nm), maximum peak height ([Rp] nm), maximum valley depth ([Rv] nm)
Arithmetic mean roughness (Ra), maximum peak height (Rp), maximum valley depth (Rv) of the resulting film
was measured using a scanning probe microscope ("SPM-9700" manufactured by Shimadzu Corporation). In dynamic mode, the measurement length in both the X and Y directions is measured in the range of 2 μm, and the obtained image is corrected (tilt, line fit, noise line removal), and then the arithmetic mean described in JIS-B0601 (1994). Obtained according to the definition of roughness.

16) Laminate strength (N/15mm)
Laminate strength was measured by the following procedure.
Procedure 1) Preparation of Laminate of Biaxially Oriented Polypropylene Film and Unstretched Polyethylene Film A continuous dry laminator was used as follows.
After gravure-coating an adhesive onto the surface layer (B) of the biaxially oriented polypropylene films obtained in Examples and Comparative Examples so that the dry coating amount is 2.8 g/m ² , it is led to a drying zone. It was dried at 80°C for 5 seconds. Subsequently, it was laminated with a sealant film between rolls provided downstream (roll pressure: 0.2 MPa, roll temperature: 50°C). The obtained laminated film was subjected to aging treatment at 40° C. for 3 days in a wound state.
The adhesive was obtained by mixing 28.9% by mass of a main agent (TM569, manufactured by Toyo-Morton Co., Ltd.), 4.00% by mass of a curing agent (CAT10L, manufactured by Toyo-Morton Co., Ltd.), and 67.1% by mass of ethyl acetate. A urethane-based adhesive was used, and a non-stretched polyethylene film (Rix (registered trademark) L4102, thickness 40 μm) manufactured by Toyobo Co., Ltd. was used as the sealant film.
Procedure 2) Measurement of laminate strength The laminate film obtained above is cut into strips (length 200 mm, width 15 mm) having long sides in the longitudinal direction of the biaxially oriented polypropylene film, and a tensile tester (Tensilon, Orientec Co.) was used to measure the peel strength (N/15 mm) when T-shaped peeling was performed at a tensile speed of 200 mm/min in an environment of 23°C. The measurement was performed three times, and the average value was taken as the laminate strength.

17) Film roll wrinkle evaluation The biaxially oriented polypropylene film thus formed was wound up with a width of 500 mm and a roll length of 1000 m, and wrinkles on the roll surface layer were visually evaluated according to the following criteria. Judgment ○ and △ were regarded as pass.
○: No wrinkles △: There are weak wrinkles, but the wrinkles disappear when a tension of about 20 N / m is applied to the pulled out film ×: There are strong wrinkles, and wrinkles remain even when a tension of about 20 N / m is applied to the pulled out film Not disappear

18) Coating suitability evaluation A butanediol vinyl alcohol copolymer (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Nichigo-G-Polymer OKS-8049) was dissolved in a 15% isopropyl alcohol aqueous solution to prepare a coating solution with a solid concentration of 5%. did. The prepared coating solution was dripped onto the surface layer (B) of the film, and the surface layer (B) of the film was coated with a Meyer bar #3 so that the dry coating amount was 0.2 g/m ² . After that, the solution was sufficiently volatilized with a dryer, and repelling of the coat layer was visually evaluated. Judgment ⊚ and ◯ were regarded as passed.
◎: No cissing of the coat layer 〇: 90% of the cissing of the coat layer is absent, but there is a slight cissing
△: Repelling of the coat layer is partially present, and the rate of no coat repelling is less than 90% ×: Repelling of the coat layer is present on the entire surface

19) Evaluation of aluminum vapor deposition film adhesion On the surface layer (B) of the film, vapor deposition was performed so that the aluminum film thickness was 30 nm using a small vacuum vapor deposition device (VWR-400/ERH, manufactured by ULVAC KIKO Co., Ltd.). . Adhesion state of the aluminum vapor deposition film was evaluated by a 90° peeling method using a 18 mm width cellotape (registered trademark) manufactured by Nichiban Co., Ltd. on the vapor deposition surface of the obtained vapor deposition film. Judgment 0 was regarded as passed.
○: No peeling of the aluminum vapor deposition film △: Partial peeling of the aluminum vapor deposition film ×: Peeling of the aluminum vapor deposition film over the entire surface

(Raw material resin)
Tables 1 to 3 show the details of polypropylene-based resin raw materials and film forming conditions used in the following examples and comparative examples.

(Example 1)
The polypropylene homopolymer PP-1 shown in Table 1 was used for the base layer (A).
Further, in the surface layer (B), 43.2% by weight of the polypropylene homopolymer PP-1 shown in Table 1, 52.0% by weight of the ethylene copolymerized polypropylene polymer PP-3 shown in Table 1, and 4.8% by weight of the masterbatch A shown in FIG. At this time, the melt flow rate (g/10 minutes) of the polypropylene-based resin composition constituting the surface layer (B) was 5.1.
For the surface layer (C), 93.6% by weight of the polypropylene homopolymer PP-1 shown in Table 1 and 6.4% by weight of the masterbatch A shown in Table 2 were blended.
Using a 45 mm extruder for the base layer (A), a 25 mm extruder for the surface layer (B), and a 20 mm extruder for the surface layer (C), the raw material resin is melted at 250 ° C. and formed into a sheet from a T die. After co-extrusion and solidification by cooling so that the surface layer (B) was in contact with a chill roll at 30°C, the film was stretched 4.5 times in the machine direction (MD) at 125°C. Then, in a tenter, both ends of the film in the width direction (TD) are clipped, preheated at 168 ° C., stretched at 155 ° C. in the width direction (TD) 8.2 times, and 6.7% in the width direction (TD). Heat set at 165° C. while relaxing. The film forming conditions at this time were defined as film forming conditions a.
Thus, a biaxially oriented polypropylene film having a structure of surface layer (B)/base layer (A)/surface layer (C) was obtained.
The surface of the surface layer (B) of the biaxially oriented polypropylene film was subjected to corona treatment using a corona treatment machine manufactured by Softal Corona & Plasma GmbH under conditions of an applied current value of 0.75 A. After that, it was wound with a winder. The thickness of the resulting film was 20 µm (thickness of surface layer (B)/base layer (A)/surface layer (C) was 1.3 µm/17.7 µm/1.0 µm).

(Example 2)
The conditions were the same as in Example 1 except that the amount of resin discharged from the extruder was adjusted so that the thickness of the base layer (A) was 15.1 μm and the thickness of the surface layer (B) was 3.9 μm. A biaxially oriented polypropylene film was obtained.

(Example 3)
The surface layer (B) contains 45.0% by weight of the polypropylene homopolymer PP-1 shown in Table 1, and 52.0% by weight of the ethylene copolymerized polypropylene polymer PP-3 shown in Table 1, as shown in Table 2. A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as in Example 1, except that the masterbatch A was blended at a rate of 3.0% by weight.

(Example 4)
The surface layer (B) contains 1.2% by weight of the polypropylene homopolymer PP-1 shown in Table 1 and 94.0% by weight of the ethylene copolymerized polypropylene polymer PP-3 shown in Table 1, as shown in Table 2. A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as in Example 1, except that the masterbatch A was blended at a rate of 4.8% by weight.

(Example 5)
The polypropylene homopolymer PP-1 used in the base layer (A) and the surface layer (C) was changed to PP-2 shown in Table 1, and the film forming conditions were changed to b shown in Table 3. Under the same conditions as in Example 1, a 20 μm biaxially oriented polypropylene film was obtained.

(Comparative example 1)
The surface layer (A) contains 60.0% by weight of the polypropylene homopolymer PP-1 shown in Table 1 and 40.0% by weight of PP-4, and the surface layer (B) contains the polypropylene shown in Table 1. A 20 μm biaxially oriented polypropylene film was prepared under the same conditions as in Example 1, except that 96.4% by weight of the homopolymer PP-1 and 3.6% by weight of the masterbatch A shown in Table 2 were blended. got

(Comparative example 2)
A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as in Example 1, except that the surface layer (B) was not subjected to corona treatment.

(Comparative Example 3)
The surface layer (B) contains 45.0% by weight of the polypropylene homopolymer PP-1 shown in Table 1, and 52.0% by weight of the ethylene copolymerized polypropylene polymer PP-3 shown in Table 1, as shown in Table 2. The conditions were the same as in Example 1, except that the masterbatch A was blended at a rate of 3.0% by weight, and only the polypropylene homopolymer PP-1 shown in Table 1 was used for the surface layer (C). to obtain a biaxially oriented polypropylene film of 20 μm.

(Comparative Example 4)
The surface layer (B) contains 47.25% by weight of the polypropylene homopolymer PP-1 shown in Table 1, and 52.00% by weight of the ethylene copolymerized polypropylene polymer PP-3 shown in Table 1, as shown in Table 2. 0.75% by weight of the masterbatch B was used, and the surface layer (C) was 98.4% by weight of the polypropylene homopolymer PP-1 shown in Table 1, and the master shown in Table 2. The conditions were the same as in Example 1, except that Batch B was blended at a rate of 1.60% by weight and the film was formed so that the surface layer (C) was in contact with the cooling roll. A system film was obtained.

(Comparative Example 5)
The base material layer (A) contains 99.0% by weight of the polypropylene homopolymer PP-1 shown in Table 1, and 1.0% of stearyl diethanolamine stearate (KYM-4K, manufactured by Matsumoto Yushi Co., Ltd.) as an antistatic agent. A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as in Example 1, except that a 20 μm thick biaxially oriented polypropylene film was used.

(Comparative Example 6)
A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as in Example 1 except that the film forming conditions were changed to c in Table 3.

Tables 4 and 5 show raw materials, manufacturing methods, and physical properties of the films used in the above Examples and Comparative Examples.

The biaxially oriented polypropylene films obtained in Examples 1 to 5 had high lamination strength, no peeling of the aluminum vapor deposition, no repelling of the coating liquid, and excellent adhesion. Moreover, the roll had no wrinkles and was excellent in blocking resistance.
On the other hand, the films of Comparative Examples 1 to 6 were all inferior in adhesiveness and roll winding state.

The biaxially oriented polypropylene film of the present invention exhibits excellent adhesion in vapor deposition, coating, and lamination with other films, has good slip properties and anti-blocking properties, and is suitable for processing stock. It is industrially useful because it can be used for food packaging and labels used for sweets and the like, and the film can be produced at low cost.

Claims (8)

A substrate layer (A) composed of a polypropylene resin composition containing a polypropylene homopolymer and/or a polypropylene resin obtained by copolymerizing an α-olefin having 4 or more carbon atoms, and one of the substrate layers (A) A surface layer (B ) is selected from the group consisting of a polypropylene homopolymer and a polypropylene resin obtained by copolymerizing an α-olefin having 4 or more carbon atoms on the surface opposite to the surface layer (B) of the base layer (A). It has a surface layer (C) composed of a polypropylene-based resin composition containing a polymer of the seed, the surface layer (B) satisfies the following (1) to (5) and (8), and the surface layer ( A biaxially oriented polypropylene film in which C) satisfies the following (6), (7), and (9).
(1) Wetting tension is 38 mN or more.
(2) The surface resistance value is 14.0 LogΩ or more.
(3) Arithmetic mean roughness (Ra) is 3.0 nm or more and 5.5 nm or less.
(4) Martens hardness is 248 N/mm ² or less.
(5) The central surface average roughness (SRa) is 0.010 μm or more and 0.026 μm or less.
(6) The center plane average roughness (SRa) is 0.020 μm or more.
(7) Martens hardness is 270 N/mm ² or more.
(8) The polypropylene-based resin composition constituting the surface layer (B) contains an antiblocking agent.
(9) The polypropylene-based resin composition constituting the surface layer (C) contains an antiblocking agent. The biaxially oriented polypropylene film according to claim 1, wherein the dynamic friction coefficient at 23°C between the surface layers (B) of the biaxially oriented polypropylene film is 0.6 or less. 3. The biaxially oriented polypropylene film according to claim 1, wherein the biaxially oriented polypropylene film has a haze value of 5% or less. The biaxially oriented polypropylene film according to any one of claims 1 to 3, wherein the maximum peak height Rp + maximum valley depth Rv of the surface layer (B) is 30 nm or more and 50 nm or less. The biaxially oriented polypropylene film according to any one of claims 1 to 4, wherein the biaxially oriented polypropylene film has an air release time of 10 seconds or less. The biaxially oriented polypropylene film according to any one of claims 1 to 5, wherein the biaxially oriented polypropylene film has a thickness of 9 µm or more and 200 µm or less. A laminate of the biaxially oriented polypropylene film according to any one of claims 1 to 6 and an unstretched polyethylene film. 8. The laminate according to claim 7, having a laminate strength of 2.0 N/15 mm or more.